ECG Guru - Instructor Resources

A gathering place for instructors of ECG and cardiac topics.

       

Subscribe to me on YouTube

Right bundle branch block

Displaying 1 - 10 of 36
Dawn's picture

Right Bundle Branch Block and More

Sat, 08/22/2020 - 15:33 -- Dawn

The Patient:    These tracings are taken from a 75-year-old man who became weak while playing golf on a very hot day.  He was pale and diaphoretic.  He was hypotensive, but we do not know his BP reading. He denies chest pain or discomfort. The patient reported a history of lung cancer and hypertension. We have no other history, and unfortunately, no follow-up information.

ECG Number 1:           The first ECG shows the standard 12 leads.  The rhythm is sinus with frequent appearances of PAC couplets.  The sinus rate varies slightly from about 76 bpm to 68 bpm, tending to slow a bit after the premature atrial contractions.  There is a right bundle branch block, and the QRS duration is about .12 seconds (120 ms). The PR interval is slightly log at 223 ms.  We do not know what medications the patient is on, and we do not have an older ECG for comparison.

There are some interesting, if subtle, changes worth mentioning.  The QRS complexes in most leads are fragmented.  That is, they have notching in the terminal S or R waves that is not due to the bundle branch block. This can be a sign of scarring, and can also be considered an equivalent to a pathological Q wave.  Speaking of pathological Q waves, they are seen in the inferior leads, II, III, and aVF.  There are also prominent, though not large Q waves in V4 through V6, leads which normally do not have them. All this points to scarring and possibly long-term coronary artery disease, with possible old M.I.  In addition, the ST segments are not entirely normal.  There is ST depression in the inferior and low lateral leads, a little ST elevation in aVL.  Also, the SHAPES of the ST segments tend to be straight throughout the ECG, instead of the usual curved (concave up) appearance.

Dawn's picture

High-grade AV Block With Bradycardia

Thu, 06/04/2020 - 14:24 -- Dawn

If you are an ECG instructor, you probably carefully choose ECGs to illustrate the topic you are teaching. One of the reasons for the existence of the ECG Guru website is our desire to provide lots of such illustrations for you to choose from.

Sometimes, though, an ECG does not clearly illustrate one specific dysrhythmia well, because the interpretation of the ECG depends on so many other factors.  In order to get it “right”, we would need to know information about the patient’s history, presentation, lab results, or previous ECGs. We might need to see the ECG done immediately before or after the one we are looking at.  Some ECG findings must ultimately be confirmed by an electrophysiology study before we can know for sure what is going on.

For those of us who are “ECG nerds”, it can be fun to debate our opinions and even more fun to hear from wiser, more advanced practitioners about their interpretations.

My belief, as a clinical instructor, is that we must teach strategies for treating the patient who has a “controversial” ECG that take into account the level of the practitioner, the care setting, and the patient’s hemodynamic status.  In some settings, it might be absolutely forbidden for a first-responder to cardiovert atrial fibrillation, for example.  But atrial fib is routinely cardioverted under controlled conditions in hospitals.  The general rule followed by emergency providers that “all wide-complex tachycardias are v tach until proven otherwise” has no doubt prevented deaths in situations where care providers did not agree on the origin of the tachycardia.

The ECG:    We do not have much patient information to go with this ECG, just that it is from a 71-year-old woman who developed severe hypotension and lost consciousness, but was revived with transcutaneous pacing.   Here is what we do know about this ECG:

·        There are regular P waves, at a rate of about 39 bpm (sinus bradycardia).

Dawn's picture

Shark Fin Pattern

Mon, 01/27/2020 - 21:54 -- Dawn

The Patient:  This ECG is from a 59-year-old woman who was found by the EMS crew to be unresponsive, with agonal respirations at about 6 breaths per minute. Her pulse was thready at the carotid, and absent peripherally. Her skin was pale, cool, and mottled.  Her BP via the monitor is 81/40, peripheral pulses not being palpable.  An initial rhythm strip showed sinus rhythm at 75 bpm with right bundle branch block and ST elevation.

The patient’s husband gave a history of “difficulty breathing” since sometime this morning, alcohol dependence, hypertension, tobacco use, and insomnia. He said she had been drinking heavily for several weeks.

She was immediately ventilated and intubated, and an intraosseous infusion line established.  A12-lead ECG was done, and it showed a dramatic change in the rhythm and ST segments over the initial strip. She was transported to a nearby hospital with CPR support. She achieved return of spontaneous circulation (ROSC) at the Emergency Department, after having three doses of epinephrine.  Follow up with the ED physician revealed that the patient had suffered a massive gastrointestinal bleed.  This patient, due to loss of a critical amount of blood, had low blood pressure and very poor perfusion, which resulted in damage to her heart (and possibly other organs as well). I do not have further follow up, but will update this if I receive more information. 

Dawn's picture

Tachycardia In An Unresponsive Patient

Tue, 08/20/2019 - 20:48 -- Dawn

 The Patient     This ECG was obtained from a 28-year-old woman who was found in her home, unresponsive.  She was hypotensive at 99/35.  No one was available to provide information about past medical history or the onset of this event.

Before you read my comments, pause to look at the ECG and see what YOU think.  We would welcome comments below from all our members!

The ECG     This ECG is quite challenging, as it illustrates the helpfulness of ECG changes in patient diagnosis, and also points out how important clinical correlation is when the ECG suggests multiple different problems. Forgive me in advance, but there is a lot to say about this ECG.

The heart rate is 148 bpm, and the rhythm is regular, although not perfectly. P waves are not seen, even though the ECG machine gives a P wave axis and PR interval measurement. The rate is fast enough to bury the P waves in the preceding T waves, especially if there is first-degree AV block. Differential dx: sinus tachycardia, PSVT, atrial flutter. The very slight irregularity points more towards sinus tachycardia.  The rate of nearly 150 suggests atrial flutter with 2:1 conduction, but the only lead that looks remotely like it has flutter waves is V2. The lack of an onset or offset of the rhythm makes it difficult to diagnose PSVT with any certainty.

Dawn's picture

Bifascicular Block With First-degree AVB

Wed, 04/24/2019 - 21:29 -- Dawn
The Patient  This ECG was obtained from an 80-year-old man with a past medical history of hypertension, diabetes, chronic obstructive pulmonary disease, hyperlipidemia, chronic kidney disease, and heart failure with preserved ejection fraction (HFpEF).

 

He presented to the hospital with a complaint of shortness of breath, and was determined to have an exacerbation of his COPD in the setting of a viral infection.  He was treated with breathing treatments and steroids, and was discharged home in improved condition.

The ECG   There is a sinus rhythm at 80 bpm.  The QRS complex is wide at .18 seconds (180 ms). The PR interval is slightly prolonged at .24 seconds (240 ms), which is first-degree AV block. There is right bundle branch block (QR in V1 and rS in Leads I and V6 with a wide QRS).  There is also a left posterior fascicular block (also called hemiblock), recognized by the right axis deviation (III is taller than aVF ).  This is bi-fascicular block, which can be chronic or acute.  There is very slight ST elevation with flattening in V1 and possibly V2.  In RBBB, “normal” T waves are directed opposite the terminal wave of the QRS.  V3 should, then, have inverted T waves. So, the upright T wave in this patient could be considered to be equivalent to an inversion in a normal ECG.  V4 through V6 have biphasic T waves, which is not normal for RBBB.  Because we do not have an old ECG, we don’t know which, if any, of these changes are chronic.  With this patient’s past medical history, it is possible for any of them to be pre-existing.

I will admit that, when I first saw this ECG, the V1 rhythm strip at the bottom looked as though there were regular P waves at a rate of about 220-240, with one buried in each QRS and one in each T wave. In scrutinizing all the other leads, I cannot find evidence for an underlying atrial tachycardia or atrial flutter, so it is probably a coincidence that the P and T “march out” with the assumption of a hidden P wave in the QRS.

Dawn's picture

Bifascicular Block

Fri, 11/16/2018 - 14:35 -- Dawn

This ECG is from a 77 year old woman who was brought to the Emergency Department by EMS. She was found to be suffering from sepsis.

ECG Interpretation      The ECG shows the expected sinus tachycardia at 123 beats per minute.  There is significant baseline artifact, of the type usually seen with muscle tension.  The artifact makes it difficult to assess P waves and PR intervals.

 

What we do see is RIGHT BUNDLE BRANCH BLOCK and LEFT ANTERIOR HEMIBLOCK, also called LEFT ANTERIOR FASCICULAR BLOCK.  Together, these are called BIFASCICULAR BLOCK.  Most people have three main fascicles in the interventricular conduction system:  the right bundle branch and the two branches of the left bundle branch, the anterior-superior fascicle and the posterior-inferior fascicle.  In bifascicular block, two of the three are blocked.

The ECG criteria for right bundle branch block are:

     *     wide QRS (> .12 seconds)

 

     *     rSR’ pattern in V1 .  (the initial R wave may be hard to see, but the QRS will be predominantly upright.

Dawn's picture

Right Bundle Branch Block With Probable Previous M.I.

Sat, 09/08/2018 - 14:35 -- Dawn

This ECG was obtained from an 87-year-old man with chest discomfort.  We have no other clinical information.

ECG Interpretation   The rhythm is regular and fast, with P waves, at 95 beats per minute. So, it is normal sinus rhythm, but the rate is probably not “normal” for this patient.  The P waves are small, and difficult to see.  We suggest Lead I to best view the P waves in this example. This is a good opportunity to teach the value of evaluating rhythm strips in more than one simultaneous lead, as subtle features may not show up well in all leads.  There is a first-degree AV block, with a PR interval of 232 ms.

We see the right bundle branch block (RBBB) pattern: rSR’ in the right precordial leads (with a tiny q wave in V1, which is not typical of  RBBB).  The QRS is wide at 148 ms (.148 seconds).  The R prime (R’) represents the right ventricle depolarizing slightly after the left ventricle.  This terminal delay widens the QRS without affecting the depolarization or contraction of the left ventricle.  This delay can be seen in every lead, but is especially easy to see in Leads I and V6, where there is a wide little s wave.  It is normal for the T waves to be in a direction opposite that of the terminal wave (inverted in Leads V1 and III, for example.)

There is left axis deviation.  The causes of LAD are many.  It is not unusual for people with RBBB to also have a left anterior hemiblock (LAH), also called left anterior fascicular block.  The left anterior fascicle has the same blood supply as the right bundle branch.   LAH causes a frontal plane axis shift – instead of Lead II having the tallest QRS of the limb leads, Leads I and aVL will be the tallest upright QRS complexes of the six limb leads.  Lead II will be very small, or flat, or negative. However, the probability of pathological Q waves in the inferior leads offers a more likely explanation for the leftward axis shift.  The M.I. that would have caused these Q waves is old, as there are no acute ST changes.  It would, of course, help to know this patient’s history.

Right bundle branch block can make evaluating for ST segment elevation a bit tricky.  Occasionally, the terminal delay – especially in Leads III and aVF – can be mistaken for ST elevation.  The J points in this ECG all appear to be at the baseline, with no overt STEMI.

 

Dawn's picture

Acute M.I. With Right Bundle Branch Block and Atrial Pacing

Wed, 01/24/2018 - 22:08 -- Dawn

This ECG was taken from a 78-year-old man who was experiencing chest pressure in the morning, after having left shoulder pain since the night before. He has a history of hypertension and hypercholesterolemia, and has an implanted pacemaker.

What does the ECG show?  The ECG shows an atrial paced rhythm, with two premature beats, beats number 5 and 12.  These are probably PVCs.  The patient has a functioning AV conduction system, so the paced atrial beats are conducting through the AV node and producing QRS complexes.  In the interventricular conduction system, the impulse encounters right bundle branch block. This causes each QRS to have an “extra” wave attached at the end, representing slightly delayed depolarization of the right ventricle.  Instead of an “rS” pattern in V1, for example, we see “rSR’ “.  The slight delay causes the QRS to be widened, as we are measuring the two ventricles separately, rather than synchronously.

There is definite ST segment elevation in V2 and V3, and the shape of the ST segment is straight, having lost it’s normal “concave upward” appearance.  In an ECG taken three minutes later, the STE extends to V4.

Do the pacemaker or the right bundle branch block prevent us from diagnosing an ST-elevation M.I.?  The answer to that is a resounding “NO!” Pacemakers can sometimes make it difficult to assess ST elevation because ventricular pacing causes ST segment changes.  Pacing the right ventricle causes a depolarization delay in the left ventricle as the impulse travels “cell to cell” across the LV.  This means an RV-paced beat will resemble a PVC from the RV.  When LV depolarization is altered, repolarization will also be altered, causing ST elevation in leads with negative QRS complexes, and ST depression is leads with upright QRSs. These are called discordant ST changes. These changes are proportionate to the height or depth of the QRS, with very minimal or no ST changes in leads with short or biphasic QRS complexes.  We don’t have to worry about that in this situation – the pacemaker is not pacing the ventricles.

Dawn's picture

Right Bundle Branch Block With Machine Interpretation Error

Tue, 09/19/2017 - 14:33 -- Dawn

Today’s ECG is from a 74-year-old man for whom we have no clinical information.  It shows a “classic” right bundle branch block.  It also shows an example of the ECG machine getting some of the interpretation wrong.  An early mistake in the interpretative algorithm caused a cascade of inaccuracies.

REVIEW of RIGHT BUNDLE BRANCH BLOCK ECG CRITERIA

     *   Supraventricular rhythm

     *   QRS .12 seconds (120 ms) in width

     *   rSR’ pattern in V1

     *   Small, wide S wave in Leads I and V6

In right bundle branch block, the initial part of each QRS complex represents the depolarization of the septum and left ventricle.  The right ventricle depolarizes late, and is represented by a terminal wave at the end of each QRS.  In V1, that terminal wave is the R’ and in I and V6 it is the small S wave. 

MACHINE MISTAKES  The first mistake the machine made was in measuring the QRS width. The machine says the QRS is .096 seconds (96 ms).  It is actually about .16 - .18 seconds.  Look at the second QRS in V1, and you will see that it extends almost the full width of a wide block (.20 sec).  It is apparent that the machine measured only the left ventricular portion of the QRS complex. Because of this error, the right bundle branch block was not noted. 

The mistake in measuring the QRS complex resulted in the machine misinterpreting the terminal wave as the ST segment.  This resulted in notations in capital letters warning of ST elevation and presence of myocardial ischemia.  The j points are actually at the baseline in all leads, indicating NO ST elevation. 

ST and T WAVE CHARACTERISTICS OF RBBB  Typically, in RBBB, the T wave will be opposite in direction from the terminal (RV) deflection.  So, when there is an R’, there will be T wave inversion.  The j point of the ST segment will not be altered, as the ST segment reflects what is happening in the LEFT VENTRICLE, which is depolarizing normally.  That means that an acute ST elevation M.I. will look the same in RBBB as it does without BBB. 

Dawn's picture

Ask The Expert

Tue, 09/19/2017 - 12:57 -- Dawn

Today’s expert is Dr. Jerry W. Jones, MD, FACEP, FAAEM

Jerry W. Jones, MD FACEP FAAEM is a diplomate of the American Board of Emergency Medicine who has practiced internal medicine and emergency medicine for 35 years. Dr. Jerry JonesDr. Jones has been on the teaching faculties of the University of Oklahoma and The University of Texas Medical Branch in Galveston. He is a published author who has also been featured in the New York Times and the Annals of Emergency Medicine for his work in the developing field of telemedicine. He is also a Fellow of the American College of Emergency Physicians and a Fellow of the American Academy of Emergency Medicine and, in addition, a member of the European Society of Emergency Medicine. 

 Dr. Jones is the CEO of Medicus of Houston and the principal instructor for the Advanced ECG Interpretation Boot Camp and the Advanced Dysrhythmia Boot Camp. 


Question:   What is the cause of an apparent right bundle branch block pattern in a paced rhythm?

Answer:  Is There a Pacemaker Wire Problem… or Not?

 During one of my orientations as a young internal medicine house officer, the cardiologist lectured to us on the essentials of how to check pacemakers. Since none of us had any ECG interpretation background our comprehension was less than sterling. But I remember him stressing the point that a properly paced pacemaker lead would result in a left bundle branch block pattern on the ECG. A right bundle branch block pattern in V1, on the other hand, meant that the pacemaker wire had inadvertently wandered into the left ventricle – a highly undesirable situation. 

“Not to worry,” he said. “Such things rarely happen and you will probably retire before seeing such a thing!” That evening I saw my first pacemaker 12-lead ECG with a right bundle branch block pattern in V1. Fate wasted no time with me.

I ordered a 3-view chest x-ray and as far as I could see, the wire looked like it was in the right ventricle where it was supposed to be. I called the cardiologist on-call who happened to be in the hospital at the time and he dropped by the ward. Back then, we didn’t have ultrasound or echo available. But he, too, was convinced the pacemaker wire was in the right ventricle. It really was and so I still hadn’t seen a RBBB pattern due to a pacer wire in the left ventricle. I still haven’t, but I have seen a number of pacemaker ECGs with a RBBB pattern in V1.

How do we know if such a finding represents a real left ventricular pacer wire or a pseudo-malplacement?

First, just be aware that a wire that really IS in the left ventricle is going to present with a RBBB pattern in V1. It will NOT ever present with a LBBB pattern. However, a wire that has been correctly placed in the RIGHT ventricle can – from time to time – present with a RBBB pattern in V1. In my years as an attending in the emergency department, I saw this seven or eight times.

Second, the axis of the pseudo-malplacement tends to demonstrate a significant left axis deviation, between -30 ° and    -90 °. Since the right ventricle is activated first, the vector finishes by pointing up and to the left. If the wire were actually located in the left ventricle, the mean frontal axis would be to the right of +90 °

Third, when we look in the precordial leads, we know that Leads V1 and V2 overlie the right ventricle and leads V5 and V6 overlie the left ventricle. Leads V3 and V4 are in between. If the pacemaker wire is in the right ventricle, whatever is causing it to have an RBBB pattern in V1 will disappear before V3. A pacemaker wire in the right ventricle will show a LBBB pattern (QS) by Lead V3. If the wire is truly in the left ventricle, the RBBB pattern will extend to V3 and usually beyond. So a quick check is this: if you see a RBBB pattern in V1 in a pacemaker patient, look at V3. If the RBBB pattern is in V3 also, the wire is truly in the left ventricle. If V3 has a predominately negative QRS (QS), the wire is safely in the right ventricle where it is supposed to be. 

A fourth check is to look for an S wave in Lead I. Remember: one of the most characteristic features of RBBB is that slurred S wave in Lead I (as well as the other left-sided leads). If the ECG shows an RBBB pattern in V1 and an S wave is present in Lead I, then that is most likely a real RBBB pattern and the wire has somehow made its way into the left ventricle.

Pseudo Malplacement of Pacemaker Wire


Pages

All our content is FREE & COPYRIGHT FREE for non-commercial use

Please be courteous and leave any watermark or author attribution on content you reproduce.

Subscribe to Right bundle branch block